not mentioned the criteria on which you're defining intelligence here, so I don't really know where to start.

However, there's a link in terms of how people seek help and socioeconomic status. People with a better quality of life are more likely to be diagnosis and treatment of a condition (any condition, pretty much).

Undiagnosed depression (along with most, if not all, mental health disorders) is more common in people with a lower quality of life.